Plumbers and Heating - Should I leave the TRV off one Radiator in the house?

sho_me_da_money

Hi Community,

Overview

I am in the midst of having all the radiators in the house bar two (in the kitchen and bathroom) being replaced. Radiators being replaced are all from the 80s and are essentially double panel rads (no fins). Following Rads are being replaced:

• Small 1.2M squared hallway radiator replaced with a stelrad double convector (K2) 600 x 600
• Living Room Radiator (this has already been replaced) with a vertical designer radiator
• Bedroom Radiators x 3 - stelrad single convector (K1) various sizes.

At the moment there is one radiator in the hallway that has no TRV on it. This is also the radiator closest one to where the smart wireless thermostat is installed.

The Problem

Since installing the living room radiator (with a vertical designer replacement), the room takes the LONGEST to warm up. What typically happens is the thermostat is static on the wall in the hallway and reaches the set temperature of 21 degrees faster than living room......and turns off the boiler. This means the living room remains cold and doesn't get any warmer as the thermostat in the hallway turns off the boiler.

When I replace the hallway 80s rad with a double panel convector that has some serious BTU, that small space is going to warm up even faster than it currently does. Remember this is the space where a radiator without a TRV is installed. 

Questions with a hope to finding the right solve

My boiler is a combi and was installed about 7 years ago (Potteron HE Plus):

- If leaving a TRV off one radiator is important, is the best way to avoid the living room staying cold to move the wireless thermostat into the living room? If I do that then the hallway is going to beaming heat as it has no TRV on it and is more powerful than the rad I am replacing. How do I control that? Should I control that?
- When I replace the hallway radiator, should I leave the TRV off the new one or should I add one to the new rad so that every rad in the house has a TRV?
- Is there a way to leave the TRV off on the new poweful radiator, leave the thermostat in the hallway and avoid the boiler going off before the living room reaches the desired temp?

The living room DOES eventually get warm if I move the thermostat to the living room.

However, it's a chicken and egg situation if I leave the thermostat on the wall in the hallway. The living room never gets to the desired temp before the boiler going off. Maybe one idea is to open the lockshield valve even further on the living room rad and turn it down on the new hallway rad?

I'd be grateful for any advice on the right solve here.

Thank you

tacpot12

You can have a TRV on every radiator, and I think I would recommend that you do so, if you have a wireless thermostat that can be moved around. You just need to turn the TRV up in the room that the wireless thermostat is in. (Turn it up to its highest setting and let the thermostat turn the boiler off when that room it up to temperature.)  

There's no way to acheive the third option that I know of. 

sho_me_da_money

Thank you tacpot. I kinda figured this would be the case. I did a small experiment under the existing (old radiators) in place. I moved the thermostat to the living room and turned the TRV to setting 4 (it goes up to 5). The room eventually warms up to the desired temp. Is there any advantage/gain/saving from moving to the TRV to the highest setting (from 4 to 5) if the desired temp is eventually reached.

So to recap your feedback is:

- Install a TRV on all radiators
- Move the wireless stat to the living room
- Pump the TRV in the living room from 4 to 5 (depends on what you say to the above question)
- Control the hallway temp by installing a TRV on it


The BG engineer that showed up a few weeks back asked "wheres the radiator with no TRV". I said I don't think there is one. He said "There MUST ALWAYS be a radiator without a TRV"..........hence my line of questioning here,.

grumbler

tacpot12 said:

You can have a TRV on every radiator, and I think I would recommend that you do so, if you have a wireless thermostat that can be moved around. You just need to turn the TRV up in the room that the wireless thermostat is in.

And if you forget to do this and all TVRs shut the flow, your heating pump will definitely not like this.

sho_me_da_money

grumbler said:

tacpot12 said:

You can have a TRV on every radiator, and I think I would recommend that you do so, if you have a wireless thermostat that can be moved around. You just need to turn the TRV up in the room that the wireless thermostat is in.

And if you forget to do this and all TVRs shut the flow, your heating pump will definitely not like this.

You mean forget to turn the TRV in the living room on or turned to full?

grumbler

sho_me_da_money said:

grumbler said:

tacpot12 said:

You can have a TRV on every radiator, and I think I would recommend that you do so, if you have a wireless thermostat that can be moved around. You just need to turn the TRV up in the room that the wireless thermostat is in.

And if you forget to do this and all TVRs shut the flow, your heating pump will definitely not like this.

You mean forget to turn the TRV in the living room on or turned to full?

To turn the TVR to the highest setting.

ETA: If you don't move the wireless thermostat around and always have it in this room it's better just to remove the head of the TVR in this room.

FreeBear

tacpot12 said: There's no way to acheive the third option that I know of. 

There is, but it is not a simple solution.

Fit smart TRVs to each radiator, and then set up a home automation system. Properly programmed, it can treat each room as a "zone" and shut down each radiator as that zone gets up to temperature.

The alternative (which should have been done in the first place) is to calculate the radiator size appropriate for each room. By the sounds of it, the "designer" radiator in the lounge is too small.

Apodemus

FreeBear said:

The alternative (which should have been done in the first place) is to calculate the radiator size appropriate for each room. By the sounds of it, the "designer" radiator in the lounge is too small.

Absolutely! It also sounds as if the hall radiator is too big!

NSG666

"The living room DOES eventually get warm if I move the thermostat to the living room."

This suggests that the radiator has sufficient output but there is an imbalance in the system but have a feel of the rad and see whether it is hot all over or just at the very top. Who has sized the replacement rads as it sounds like the output of the hall rad is already way over requirements and the new one has an even higher output?

Also, the balance of water circulation through the system might need tweaking to give a more even distribution of heat throughout the house. You could get a good heating engineer to correctly size the radiators and properly balance the system and leave the hive in the hall and/or put lock-shield valves on the living room rad and put the hive in there with trv's on all the others.

Chickereeeee

Wouldn't fitting an automatic bypass valve (if not there already) solve the problem?

Also, restricting the flow to the hall radiator by using the lockshield valve will make it slower to warm up.

Bendy_House

Hi smdm.

You clearly have a decent overall understanding of what's going on, but with a few small gaps  

The principle is; one rad(s) - in the room with the wall 'stat - is not fitted with a TRV, so it is set manually to provide the 'right' amount of heat to allow that room to get up to the required temp, whilst also allowing all the other rads to also get up to temps to suit their rooms. Ie, all the rads in the house should be emitting 'matching' amounts of heat to suit their individual rooms; smaller rooms require smaller rads (or rads turned down to be less powerful).

Since this 'balancing act' cannot be done perfectly, and since different rooms will also be wanting different temps at different times, all the rooms, bar one, are also fitted with TRVs. These are used to automatically control the heat in each room. Obviously, they can only do this if the boiler is running, and the boiler will only be running when the 'main' room - the one with the wall stat - is telling the boiler to be running. So it's important for this 'main' room to be 'balanced' at the same level.

A well-balanced system should allow each room to warm up to their required temps at the same time. Clearly not an exact science, so that's why rads have 'lockshield' valves at the opposite ends to their control valves (such as TRVs) so they can be balanced. Ie, if one rad is outputting far too much heat compared to the others - at the moment, this is your hall rad! - then the 'lockshield' is closed off a part-turn until that rad's output is what's required for that room, and I'd suggest your hall should only be getting to around 18oC.

It sounds as tho' your rad replacements may have been a bit haphazard - some rooms with oversized rads, some perhaps undersized. Not ideal, but you can make an 'oversized' rad behave like a normal or even undersized rad by closing off this lockshield. Once set, the lockshield is left alone, and all the actual heat output controlling will then be done by the TRVs.

So - lockshields are used to make each rad suit their individual rooms, so that all the rads heat up evenly to provide the right amount of heat for each room at the same time. You could fit a 2m triple-panel rad in a tiny bathroom, but close off its lockshield so it acts like a towel rail. You'd be daft to, of course, but you get the idea?

At the moment, then, it seems as tho' your sitting room's rad - the designer type - is a little underpowered? Ie, it will get the room up to temp, but it takes longer than you'd like? The answer is to turn (lockshield) all the other rads down so that they, too, heat up their rooms at the same 'slow' rate! (Assuming the sitting room's rad cannot be opened up more with the lockshield to make it more powerful?).

Does this make sense? If you have 10 rads in 10 rooms, 9 of which are large rads and one small, then to make them heat up at the same rate, you need to turn the other 9 rads down so they match the smallest. This doesn't usually need to happen, of course, because normally rads are chosen correctly so their size matches their rooms.

It will definitely need doing to your hallway rad - that sounds as tho' it's far too big for that room. So it'll need tweaking down to make it a 'smaller' rad.

And, yes, the best room in which to have the room stat (and the non-TRVs) is the sitting/living area, because, frankly, every other room is secondary to this.

And, yes, once the room-stat room gets up to temp, the boiler will be turned off so all the rads will cool down slowly. But that's fine, and as it should be.

What to do, then?

(1) Remove the TRV head - or just open it up to max - on the vertical sitting room rad. Check that it comes on 'piping hot' when the CH is on. What is your boiler CH flow temp at? 70oC? In which case the sitting room rad should be too hot to touch. Is it? Or are other rads hotter to the touch?

(2) Move the room stat to the sitting room, and set it to whatever temp you want in there - 20 or 21oC for example.

(3) Fit a TRV to the hallway rad, and set it to between 2 and 3 (~18oC). If that rad still heats up faster than others (especially the sitting room rad), then its lockshield will likely need closing down a quarter-turn to make it a 'less-powerful' rad.

(4) Set every other TRV in the house to suit their rooms - eg 2-3 for bedrooms, tho' you might want to turn them right down during the day. Monitor these rooms too, when the CH comes on. See how quickly they get up to their temp. (Bear in mind that the TRVs will shut them off when their set temp is reached.) At its crudest, see if some rads become 'piping' at an obviously faster rate than others when the CH is turned on.

Monitor this, and see how it goes.

A note about 'balancing' rads. This should have been done by the installer of the rads, and is done 'properly' by measuring the temps at each end of the rad - the pipes that supply them. You are looking for something like an 11oC difference (loss) in temp between the flow and return ends. I'm not sure many plumbers go this far. But, when they do, you'll usually find that the lockshield valve will be close to being 'off', perhaps one or two turns open from the fully-closed position. To adjust them then should be done in tiny steps, a quarter-turn max either way, and the effect monitored (which can take a while). You should also know - note down - the starting positions of each one so you can always return to it. If you are going to try this, then the starting point should be;

(a) Pull off the plastic cap.

(b) Note down which way the spindle is directed - you can mark it with a pen, or attach a paper 'flag' to note this. Write it down.

(c) Turn it clockwise until fully closed, noting every turn and part-turn. Write this down - it's your starting point.

(d) Return it to your starting point.

(e) To adjust the balance, the TRVs should all be open. Then try tweaking down one lockshield at a time, by a quarter-turn in the direction required - clockwise (closed) if the rad is too powerful. And vicky-verka. 

(f) Monitor the results.

If you want to come back with some figures - the positions of the lockshields in the hallway and sitting room rads - we may be able to suggest some tweaks. The important thing to note is, as long as you've recorded the starting points, you can always return to them, so now't lost.